Metal studs are often used for frame structures of e.g. separation walls or so called dry walls. The metal studs are provided with punched holes in their web for passing through pipes, wiring, cabling and the like. Grommets are provided to be placed in the stud holes to guide the pipes, wiring, cabling and the like through said holes in the stud and to protect them from damage by the edge of the holes.
There are known grommets which snap into a punched hole and are sized to fit the hole. These grommets have a cylindrical body with a flange on one end and spring snaps on the body, such that the body can be inserted in the stud hole and the edge of said hole snaps behind the spring snaps to be caught between the flange and the spring snaps.
U.S. Pat. No. 5,537,714 shows a plastic grommet for use on metal studs in a wall construction for protecting cables, conduits or wires. This known grommet has a cylindrical body with a radial flange. On the outer surface of the cylindrical body are provided radially projecting spring snaps The cylindrical body can be fit into a sized hole in the web of the stud such that the flange engages the web of the stud such that the edge of the hole in the web is captured between the spring snaps and the flange. This particular grommet also has spring fingers on the other side of the flange and holes in the flange which allows to join the grommet to a same grommet flange-to-flange. The two grommets thus assembled on opposite sides of a rectangular or other irregular or pre-punched hole in the stud web capture the web between the flanges. This known plastic grommet is suitable for guiding relatively long pipes through the holes in the studs of a wall construction. However, it has as a disadvantage that vibrations in the installed pipes are transferred into the studs via the grommets.
U.S. Pat. No. 4,656,689 discloses a grommet which is particularly developed for passing conduits of automotive air conditioning systems through a firewall which separates the engine compartment and the passenger compartment of the vehicle. This known grommet is for protecting a conduit passing through a wall opening and for providing an air seal between the conduit and the edges of the wall around the wall opening. The grommet has a relatively stiff fastener portion with a washer shaped base portion having a centrally located circular opening. The fastener portion has projections extending from the base portion and locking devices at the ends of the projections for engaging the edges of the wall around the wall opening. The grommet furthermore has an elastomeric seal portion, which has a pan and a flange, said pan having a central aperture of smaller dimension than the outside dimension of the conduit, whereby a seal around the perimeter of said conduit is formed when said conduit is passed through said aperture. When installed, the pan extends through the central opening in the base portion of the fastener portion and through the opening in the wall. The flange of the elastomeric seal portion has openings which receive the projections of the fastener portion. When installed the flange of the elastomeric seal portion is located between the wall and the base portion of the fastener portion. It is to be expected that the elastomeric part isolates vibrations in the conduit. However, this grommet is not suitable for passing through long lengths of pipe in a wall construction, because the elastomeric part would engage directly and narrowly on the pipe, which hampers passing the pipe through the grommet. This disadvantage becomes even more apparent when the pipe has to be guided through a number of grommets in a wall structure which in practise will be the case.
U.S. Pat. No. 5,765,819 discloses a vibration isolating grommet comprising a metal flanged cylindrical sleeve and an annular elastomeric element having a cylindrical portion and a flange section. On the end of the cylindrical portion of the elastomeric element an axially extending portion is provided with a relatively large radially inwardly extending truncated conical lip at the extremity thereof. By insertion of the metal sleeve in the elastomeric element and axially advancing the metal sleeve, radially outward movement of the conical portion of the elastomeric element is effected. Thereby, when the grommet is inserted in an aperture in a work piece, the outwardly moved conical portion underlies a bottom surface of the workpiece (plate) to retain the grommet in the aperture in a pre-assembly state. The inside diameter of the sleeve is sized to freely accept a mounting fastener, e.g. a bolt The head of the bolt rests on the flange of the metal sleeve. By tensioning the fastening element with regard to a support structure the flange section elastomeric element is compressed between the flange of the metal sleeve and the workpiece. The other end of the metal sleeve abuts the support structure thereby limiting the compression of the flange section of the elastomeric element. This known grommet is typically designed for passing through fastening elements such that a workpiece can be mounted to a support in a vibration isolated manner. Although the grommet can be retained in a pre-assembly state in an aperture in a workpiece, it is not suitable for passing through pipes since the retaining force of the elastomeric lips is not sufficient to withstand the forces when long pieces of pipe are passed through the grommet Furthermore the known grommet will only be retained in a sized aperture which is closely adapted to the size of the grommet.
The present invention has for an object to provide a grommet for a hole in a metal stud which provides isolation of vibrations from the pipes to a stud of a wall structure
Another object is to provide a grommet which allows to apply the grommet with studs with differently shaped and sized apertures.
Yet another object of the invention is to provide a grommet which allows low friction sliding of pipes through the grommet.